The arrests were the result of an "unprecedented" six-month operation, the NCA said, and involved police forces across England, Wales, Scotland and Northern Ireland.
At least 400 children had been protected as a result, the agency said.
Charges had not yet been finalized in most cases, but some had already been charged with offences ranging from the possession of indecent images of children to serious sexual assault.
"Some of the people who start by accessing indecent images online go on to abuse children directly," said NCA deputy director general Phil Gormley.
"So the operation is not only about catching people who have already offended - it is about influencing potential offenders before they cross that line," he said.
"We want those offenders to know that the internet is not a safe,a nonymous, space for accessing indecent images, that they leave a digital footprint, and that law enforcement will find it."
DPA